This invention relates to a class of metal complexes, the ligands used to prepare these metal complexes and to olefin polymerization catalysts derived therefrom that are particularly suitable for use in a polymerization process for preparing polymers by polymerization of xcex1-olefins and mixtures of xcex1-olefins.
Constrained geometry metal complexes and methods for their preparation are disclosed in U.S. Pat. No. 5,703,187; U.S. Pat. No. 5,321,106; U.S. Pat. No. 5,721,185; U.S. Pat. No. 5,374,696; U.S. Pat. No. 5,055,438; U.S. Pat. No. 5,057,475; U.S. Pat. No. 5,096,867; U.S. Pat. No. 5,064,802; U.S. Pat. No. 5,132,380; U.S. Pat. No. 5,470,993, as well as EP-A-514,828, and elsewhere.
U.S. Pat. No. 5,350,817 and U.S. Pat. No. 5,304,614 disclose bridged zirconocene complexes, wherein two indenyl groups are covalently linked together by a bridge containing carbon or silicon, which are useful for the polymerization of propylene.
EP-A-577,581 discloses unsymmetrical bis-Cp metallocenes containing a fluorenyl ligand with heteroatom substituents.
E. Barsties; S. Schaible; M.-H. Prosenc; U. Rief; W. Roll; O. Weyland; B. Dorerer; H.-H. Brintzinger J. Organometallic Chem. 1996, 520, 63-68, and H. Plenio; D. Birth J. Organometallic Chem. 1996, 519, 269-272 disclose systems in which the cyclopentadienyl ring of the indenyl is substituted with a dimethylamino group in non-bridged and Si-bridged bis-indenyl complexes useful for the formation of isotactic polypropylene and polyethylene.
Disclosure of random heteroatom substitution in mono-Cp metallocenes is found in EP-A-416,815, WO 95/07942, WO 96/13529, and U.S. Pat. No. 5,096,867 and U.S. Pat. No. 5,621,126. Specific heteroatom substitution of the 3- and 2-position of indenyl complexes of group 4 metals was disclosed in WO 98/06727 and WO/98/06728 respectively. The foregoing specifically substituted metal complexes have produced improved catalyst results, however, problems still remain with catalyst efficiency and deactivation of the catalyst under high temperature polymerization conditions. It would be advantageous to be able to produce polyolefins with higher molecular weights. It would also be advantageous to be able to improve other physical characteristics of the polymers produced by altering the substitution around the cyclopentadienyl group of the metallocene complexes used in olefin polymerization catalyst systems.